Apparently I was wrong but it is just because it is not the Urdu way of saying things; a person cannot be 'an influence' on someone, rather a person's influence on someone can be good or bad or whatever.

Post 4 rather denotes "company", whereas the question is more about "influence." One need not be in constant company of someone to have someone's influence dripping upon us. Hence, I would rather go for post 7, but I would rather rephrase: "uskaa tum par achchhaa asar paR/Dal rahaa hai" or something like that.

Sorry Alfaaz SaaHib, mu2assar/mu2assir aside, I can't get my head round your sentence. It is most likely me. Without nek/bad, I would take it as "He is effective for/on you" but I don't know what to make of it with "nek/bad".